Ice Makers
 
Ice Makers
Why Should I Care?

More than a million ice makers operate in restaurants, hospitals, hotels, and other facilities. Together they consume more than 8 billion kilowatt-hours (kWh) of electricity each year. These energy-hungry machines cost businesses more than $600 million in annual utility bills. Much of that spending is unnecessary, as there is a large model-to-model variation in the amount of electricity used！anywhere from 4 to 22 kWh per 100 pounds of ice produced. The bottom line? Careful choice of equipment can lead to big energy savings.

Types of ice. Ice machines produce a variety types of ice for a range of applications.
The choices are:

Cube ice, which is clear and comes in various shapes--rectangular, crescent, pillow-shaped, pure cube, or other regular shapes. The largest dimension is about 1 1/4 inches. Pieces of ice range in weight from 1/6 to 1/2 ounce and contain minimal amounts of liquid water. Most ice machines make cube ice.
Flake ice comes in chips or flakes that contain up to 20 percent liquid water. Flake ice tends to conform to the surface of items that rest on it and is typically used in supermarket display cases, on fishing boats, or anywhere food needs to be preserved for short periods. Flake ice may also occasionally be used in soft drinks.
Crushed ice consists of small, irregular pieces made by crushing larger chunks of ice. Its primary use is for keeping drinks cool.
Ice nuggets, made by extruding and freezing slushy flake ice into small pieces, are also used primarily to cool drinks.

For a detailed list of what types of ice are preferred for different applications, see page 50 of the 1998 ASHRAE Refrigeration Handbook. Information about ASHRAE publications is available at www.ashrae.org.

Types of machines. Ice machines may be integrated with an insulated storage bin (see Figure 1), known as a self-contained unit, or mounted on top of a separate bin. Integrated units are the simplest to install, but usually come with a fixed capacity. The capacity of nonintegrated units can be increased by stacking additional ice-making machinery on top of the first machine or by placing a second machine next to the first on top of a larger bin.

Figure 1: Ice cube maker
Ice cube makers often come with the ice-making equipment integrated with the storage bin, as shown here. Stainless steel resists corrosion and provides an attractive appearance.
Source: Manitowoc Co.

Ice makers are also classified as batch or continuous in operation. Batch models tend to produce ice that is purer than its source water, since the freezing process separates out the impurities. In continuous units, chemicals tend to remix in an ice/water combination. Controls for batch ice makers are more complicated！they must end the freezing at the proper time to start a thawing cycle, and resume the freezing process after the ice has been harvested.

Types of condenser. Ice makers are available with three different types of condenser:

Air-cooled ice makers use the most energy！about 5.4 to 22.5 kWh per 100 pounds of ice！but are less expensive than water-cooled models and use less water.
Water-cooled models are more efficient than air-cooled units, using 4.7 to 14.2 kWh per 100 pounds of ice. There is no addition to air conditioning loads, because the heat removed in making the ice is discharged outside the building.
Remote air-cooled condensers transfer heat generated by the ice-making process outside of the building. Like water-cooled units, they reject heat outside of conditioned spaces and therefore do not increase air conditioning loads. They also reduce noise levels inside by up to 75 percent, but there are extra installation costs for running lines to a remote location.

Types of bins. Ice storage bins are available in a range of sizes, usually with a full-width door allowing user access to the ice. Bins are usually sized to hold 10 to 12 hours worth of ice production. Larger bins are available for such applications as supermarket displays for which ice is only changed once or twice a week. Sealed, sanitary units are also available, but they're much more expensive than standard units. They are often used in hospitals, motels, and restaurants and for any operations in which ice comes in direct contact with food or drink.

Water heat recuperation. Some ice makers direct the incoming water behind the evaporator plate or over the ice to use the heat of the incoming water to assist in the ice harvesting process. This step also serves to prechill the incoming water and cuts energy use significantly.

Water treatment system. Ice makers can be run directly from tap water supplies, but some applications may require additional water treatment. In general, if the total chemical content of the incoming water is greater than 400 ppm, auxiliary water treatment is recommended.

Self-cleaning. A relatively new option among ice makers is the self-cleaning machine. Typically, ice makers are cleaned and sanitized every 2 to 6 weeks, which requires emptying the bin of ice, adding cleaning solution, switching the controls to a cleaning mode that circulates the cleaning solution through the machine, and then producing enough ice to be sure the machine is cleared of the solution. Self-cleaning models automate most of these steps.

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How to Make the Best Choice

Estimate the cost-effectiveness of picking an energy efficient unit. The U.S. Federal Energy Management Program (FEMP) has published a list of recommended and best available energy efficiency levels for different types of ice makers. The data can be found on the FEMP Web site at . The sample calculation in Table 1 shows how to compute energy savings that result from choosing a more efficient model and the payback period.

Table 1: Calculating ice-maker cost-effectiveness

Ice makers are available in a wide range of efficiencies. The base model in the sample calculation is the least efficient ice maker available in the class of ice makers that make 800 pounds per day. Selecting a model that provides the efficiency level recommended by FEMP would save $213 per year over the least efficient model. If the incremental cost for the recommended level was $500, the ice maker would pay for itself in just under three years. The calculations assume an electricity cost of $0.08/kWh.

Item
Base model
Recommended level
Best available

Energy use (kWh/100 lbs of water)
8
5.8
5.4

Annual energy use (kWh)
8,000
5,800
5,400

Annual energy cost ($)
640
467
427

Annual energy savings ($)
NA
173
213

Purchase price ($)
2,300
2,800
3,000

Incremental cost ($)
NA
500
700

Payback period (years)
NA
2.9
3.3

NA = not applicable

Source: Platts

Determine required capacity. Determining the required capacity of an ice-making machine is based on rules of thumb developed over years of experience. Manufacturers provide sizing guidelines to help users pick the most economical combination of ice maker and storage bin. The guidelines are based on the type and size of the application. For example, an ice maker for soft drinks in a fast food restaurant might be expected to be in service seven days a week at its average level of ice production, and have to produce ice at a peak rate of 150 percent of average for two days. Under those conditions, the machine should be sized to provide 0.25 to 0.5 pounds per customer.

Pick a machine with the right capacity. Oversizing of ice makers can increase energy consumption due to excessive standby losses, so pick a unit that most closely matches your quantity requirements. Ice machines are designated by the amount of ice that they can produce in a 24-hour period, under reference conditions of 70oF ambient temperature and 50oF inlet water temperatures. Typical sizes are 250, 400, 500, 650, 800, 1,000, 1,200, and 1,400 pounds per 24 hours, but machines are available that make up to several tons of ice per day. Actual capacity varies with both ambient temperature and water temperature. Manufacturers usually recommend using the capacity listed at the test conditions used by the Air-Conditioning and Refrigeration Institute (ARI)！ 90oF ambient air and 70oF water. Selecting equipment based on the capacity at those conditions will ensure that adequate ice can be produced under most conditions encountered in operation.

ARI publishes a directory called "Certified Automatic Commercial Ice-Cube Machines and Ice Storage Bins." Information about ARI publications is available on the Web at .

Pick a unit with appropriate noise level. The noise level of icemakers is typically equal to that of a window air conditioner, which is acceptable for most applications. In some cases, lower levels may be desirable, and the buyer should ensure that the manufacturer can provide equipment that meets those requirements.

Pick a reliable unit. Most purchasers of ice-making machines choose them as much for reliability as efficiency or first cost. Although reliability data for specific equipment are not available, you can make a sound choice by looking for equipment with the fewest moving parts and with controls that include diagnostic capabilities. In addition, two small machines rather than one large one can provide more availability.

Look for an easy-to-maintain model. Even the most reliable ice makers require a lot of maintenance if they are to last more than a few years. Regular cleaning and sanitation treatments are necessary of both the ice storage and ice-making parts. Therefore, the best bet is to go with equipment that includes clear, simple installation and maintenance instructions and procedures.

Look at water costs in areas where water is expensive. A hundred pounds of ice is equal to about 12 gallons of water. The amount of water used to make this amount of ice varies widely, in the range of 13 to 35 gallons. The extra water is used for melting and releasing the ice and keeping the equipment operating smoothly and cleanly. Where water prices are average, water cost for ice making is less than 30 percent of the electricity cost. But in areas where water is expensive, water use may be an important consideration.

There is also a connection between water use and maintenance costs. Some self-cleaning machines use three times as much water as standard models, but they save on labor costs. Higher water consumption also reportedly improves overall machine reliability by keeping components (the water pump, for example) free of scale and by keeping the evaporator clean. Unfortunately, no data are available precisely correlating water use and maintenance costs. If water costs are high in your area, ask equipment manufacturers about water-conserving options.

Manufacturers have been focusing on improving controls and diagnostics. One product released in mid-2000 records a series of sounds that help technicians diagnose equipment problems. Another new product monitors gearbox activity and shuts the machine down if the gearbox is overworked.

Manufacturers have not focused on improving efficiency of their products, because they don't consider energy efficiency to be a market driver. Nevertheless, the compressors, which consume more than 90 percent of the energy an ice maker uses, are standard refrigeration compressors！so as compressor technology improves in general, look for more efficient ice makers as well.